1. Field of the Invention
The present invention relates to a diagnostic apparatus for an evaporated fuel system, and relates to a vehicle control apparatus for an automotive vehicle equipped with the diagnostic apparatus. In the evaporated fuel system, fuel vapor, which is evaporated from fuel within a fuel tank, is adsorbed in a canister, and the adsorbed fuel vapor is purged from the canister into an intake passage of an internal combustion engine via a purge passage by using a negative pressure in the intake passage of the engine.
2. Description of the Related Art
As disclosed in Japanese Laid-Open Patent Application No. 9-303214, an evaporated fuel system that is designed to prevent the fuel vapor of a fuel tank from escaping into the atmosphere is known. In the evaporated fuel system, the fuel vapor, which is evaporated from fuel within the fuel tank, is adsorbed in a canister, and the adsorbed fuel vapor is purged, at a proper time, from the canister into an intake passage of an internal combustion engine via a purge passage by using a negative pressure in the intake passage of the engine.
If a leakage-type malfunction, such as pipe disconnection, pipe cracking or fuel tank cracking, occurs in the evaporated fuel system, the fuel vapor will leak from the location of the malfunction. In order to suitably achieve the above-described operation of the evaporated fuel system, it is necessary to safely detect whether the leakage-type malfunction occurs in the evaporated fuel system.
A conceivable diagnostic method for detecting a leakage-type malfunction in the evaporated fuel system is as follows. (1) A negative pressure in the intake passage of the engine is introduced into the evaporated fuel system so as to reduce the pressure in the evaporated fuel system. (2) After the pressure in the evaporated fuel system reaches a reference pressure, the evaporated fuel system is isolated by closing the purge passage. (3) A change in the pressure in the evaporated fuel system after the system is isolated is monitored and the determination as to whether a leakage-type malfunction occurs in the evaporated fuel system is performed based on the monitored pressure change.
When the result of the monitoring is that the pressure of the isolated evaporated fuel system is rapidly increased to the atmospheric pressure, it is determined that a leakage-type malfunction does occur in the evaporated fuel system. On the other hand, when the result of the monitoring is that the change, in the pressure of the isolated evaporated fuel system is negligible, it is determined that no leakage-type malfunction occurs in the evaporated fuel system. Hence, by using the above diagnostic method, it is possible to determine whether the leakage-type malfunction occurs in the evaporated fuel system.
However, when the negative pressure in the intake passage of the engine is not sufficiently large to reduce the pressure in the evaporated fuel system, the internal pressure of the evaporated fuel system is not smoothly reduced. In such a case, the internal pressure of the evaporated fuel system may not reach the reference pressure, or much time is needed for the pressure in the evaporated fuel system to reach the reference pressure. During the period for which the negative pressure in the intake passage of the engine is being introduced into the evaporated fuel system, the adsorbed fuel vapor cannot be properly purged from the canister into the intake passage via the purge passage. Therefore, when the above diagnostic method is executed under the condition in which the negative pressure in the intake passage is not sufficiently large, the evaporated fuel system is placed in the non-purging condition for a considerably long time. This will result in the deterioration of the evaporative emission of the engine.
To eliminate the above problem, in the evaporated fuel system disclosed in Japanese Laid-Open Patent Application No. 9-303214, when the negative pressure in the intake passage of the engine is not sufficient large to reduce the internal pressure of the evaporated fuel system, or when the elapsed time needed for the pressure in the evaporated fuel system to reach the reference pressure is longer than a predetermined time, the execution of the above diagnostic method is inhibited or terminated. However, the execution of the diagnostic method according to the above-mentioned document is always inhibited or terminated when the negative pressure in the intake passage is not sufficiently large.
Further, there is no teaching in the above-mentioned document of positively maintaining the negative pressure of the intake passage that is sufficiently large in magnitude to reduce the internal pressure of the evaporated fuel system, when introducing the negative pressure of the intake passage into the evaporated fuel system to reduce the system pressure. If the negative pressure of the intake passage that is sufficient large in magnitude can be maintained when introducing the negative pressure of the intake passage into the evaporated fuel system, it is possible to avoid the undesired condition in which the evaporated fuel system is placed in the non-purging condition for a considerably long time, without inhibiting or terminating the execution of the diagnostic method.
In order to overcome the above-described problems, preferred embodiments of the present invention provide an improved evaporated fuel system diagnostic apparatus which is capable of maintaining the negative pressure of the intake passage that is sufficiently large in magnitude to reduce the internal pressure of the evaporated fuel system to a reference pressure, when introducing the negative pressure of the intake passage into the evaporated fuel system.
Another object of the present invention is to provide a vehicle control apparatus for an automotive vehicle equipped with the evaporated fuel system diagnostic apparatus which maintains the negative pressure in the intake passage that is sufficiently large in magnitude to reduce the internal pressure of the evaporated fuel system to a reference pressure, when introducing the negative pressure of the intake passage into the evaporated fuel system.
According to one preferred embodiment of the present invention, an evaporated fuel system diagnostic apparatus includes: a malfunction determination unit which determines whether a malfunction in the evaporated fuel system occurs, by introducing a negative pressure of an intake passage of an internal combustion engine into a fuel tank; and an operating condition setting unit which sets, when the malfunction determination unit has started the introduction of the negative pressure of the intake passage into the fuel tank, an operating condition of the engine in a predetermined condition that causes the negative pressure of the intake passage to be within a predetermined pressure range.
In the evaporated fuel system diagnostic apparatus of the above preferred embodiment, the operating condition of the engine is set, when introducing the negative pressure of the intake passage into the evaporated fuel system, in the predetermined condition that causes the negative pressure of the intake passage to be within the predetermined pressure range. As the engine operating condition is set in the predetermined condition, the setting of the throttle valve at a large opening angle is avoided, regardless of whether a heavy load on the engine is demanded by the vehicle operator.
According to one preferred embodiment of the present invention, a diagnostic apparatus for an evaporated fuel system in which fuel vapor, evaporated from fuel within a fuel tank, is adsorbed, and the adsorbed fuel vapor is purged into an intake passage of an internal combustion engine via a purge passage by using a negative pressure of the intake passage, includes: a malfunction determination unit which determines whether a malfunction in the evaporated fuel system occurs, based on an internal pressure in the evaporated fuel system after the evaporated fuel system pressure reaches a reference pressure by introduction of the negative pressure of the intake passage into the fuel tank; and an upper-limit changing unit which changes, when the malfunction determination unit performs the determination regarding the malfunction, an upper-limit value of an opening angle for a throttle valve to a second upper-limit value that is smaller than a first upper-limit value of the throttle valve opening angle used when the malfunction determination unit does not perform the determination.
In the evaporated fuel system diagnostic apparatus of the above preferred embodiment, the upper-limit value of the opening angle for the throttle valve is changed, when introducing the negative pressure of the intake passage into the evaporated fuel system, to a second upper-limit value that is smaller than the first upper-limit value used for the throttle valve in a normal operating condition. As the upper-limit value of the throttle opening angle is changed to a smaller value, the setting of the throttle valve at a large opening angle is avoided, regardless of whether a heavy load on the engine is demanded by the vehicle operator.
According to one preferred embodiment of the present invention, a diagnostic apparatus for an evaporated fuel system in which fuel vapor, evaporated from fuel within a fuel tank, is adsorbed, and the adsorbed fuel vapor is purged into an intake passage of an internal combustion engine via a purge passage by using a negative pressure of the intake passage, includes: a malfunction determination unit which determines whether a malfunction occurs in the evaporated fuel system, based on an internal pressure in the evaporated fuel system after the evaporated fuel system pressure reaches a reference pressure by introduction of the negative pressure of the intake passage into the fuel tank; a pressure introduction unit which introduces the negative pressure of the intake passage into the fuel tank to cause the evaporated fuel system pressure to reach the reference pressure; and a time counting unit which determines an elapsed time from a start of the introduction of the negative pressure, during which an internal pressure in the intake passage is less than a threshold value, wherein the malfunction determination unit determines whether the evaporated fuel system pressure reaches the reference pressure, based on whether the elapsed time, determined by the time counting unit, reaches a reference time.
According to one preferred embodiment of the present invention, a diagnostic apparatus for an evaporated fuel system in which fuel vapor, evaporated from fuel within a fuel tank, is adsorbed, and the adsorbed fuel vapor is purged into an intake passage of an internal combustion engine via a purge passage by using a negative pressure of the intake passage, includes: a malfunction determination unit which determines whether a malfunction occurs in the evaporated fuel system based on an internal pressure in the evaporated fuel system after the evaporated fuel system pressure reaches a reference pressure by introduction of the negative pressure of the intake passage into the fuel tank; and a pressure introduction unit which introduces the negative pressure of the intake passage into the fuel tank to cause the evaporated fuel system pressure to reach the reference pressure, wherein the malfunction determination unit determines whether the evaporated fuel system pressure reaches the reference pressure, based on whether an elapsed time, counted from a start of the introduction of the negative pressure, reaches a reference time, and interrupts, when an internal pressure in the intake passage after the start of the introduction of the negative pressure exceeds a threshold value, the counting of the elapsed time.
According to one preferred embodiment of the present invention, a diagnostic apparatus for an evaporated fuel system in which fuel vapor, evaporated from fuel within a fuel tank, is adsorbed, and the adsorbed fuel vapor is purged into an intake passage of an internal combustion engine via a purge passage by using a negative pressure of the intake passage, includes: a malfunction determination unit which determines whether a malfunction occurs in the evaporated fuel system, based on an internal pressure in the evaporated fuel system after the evaporated fuel system pressure reaches a reference pressure by introduction of the negative pressure of the intake passage into the fuel tank; a pressure introduction unit which introduces the negative pressure of the intake passage into the fuel tank to cause the evaporated fuel system pressure to reach the reference pressure, wherein the malfunction determination unit determines whether the evaporated fuel system pressure reaches the reference pressure, based on whether a total of a flow rate of the purged fuel vapor counted from a start of the introduction of the negative pressure reaches a reference count, and resets, when an internal pressure in the intake passage after the start of the introduction of the negative pressure exceeds a threshold value, the total of the flow rate to zero.
According to one preferred embodiment of the present invention, a diagnostic apparatus for an evaporated fuel system of an automotive vehicle equipped with an internal combustion engine and a secondary power source includes: a malfunction determination unit which determines whether a malfunction occurs in the evaporated fuel system, by introduction of a negative pressure of an intake passage of the engine into a fuel tank; an operating condition setting unit which sets, when the malfunction determination unit has started the introduction of the negative pressure of the intake passage into the fuel tank, an operating condition of the engine in a predetermined condition that causes the negative pressure of the intake passage to be within a predetermined pressure range; and an output force changing unit which increases, when the operating condition setting unit has set the operating condition of the engine in the predetermined condition, an output force of the secondary power source by an amount corresponding to a decrease of an engine output force calculated with respect to the engine operating condition that is set in the predetermined condition.
It is possible for the evaporated fuel system diagnostic apparatus of the present invention to maintain the negative pressure of the intake passage that is sufficiently large to reduce the internal pressure of the evaporated fuel system. The evaporated fuel system diagnostic apparatus of the present invention is effective in quickly reducing the pressure in the evaporated fuel system to the reference pressure for the determination of the occurrence of a malfunction in the evaporated fuel system.
Further, according to one preferred embodiment of the present invention, a vehicle control apparatus for an automotive vehicle equipped with an internal combustion engine, a secondary power source, an evaporated fuel system and an evaporated fuel system diagnostic apparatus, wherein the evaporated fuel system diagnostic apparatus includes: a malfunction determination unit which determines whether a malfunction in the evaporated fuel system occurs, based on an internal pressure produced in the evaporated fuel system after a reference pressure is reached by the evaporated fuel system pressure by introduction of a negative pressure of an intake passage of the engine into a fuel tank; and an upper-limit changing unit which changes, when the malfunction determination unit performs the determination regarding the malfunction, an upper-limit value of an opening angle for a throttle valve to a second upper-limit value that is smaller than a first upper-limit value of the throttle valve opening angle used when the malfunction determination unit does not perform the determination, and the vehicle control apparatus includes an output force changing unit which increases, when an output force of the engine is decreased after the upper-limit changing unit changes the upper-limit value of the throttle valve opening angle to the second upper-limit value, an output force of the secondary power source by an amount corresponding to the decrease of the engine output force.
In the vehicle control apparatus of the above preferred embodiment, the output force of the secondary power source is increased by the amount corresponding to the decrease of the engine output force after the upper-limit value of the throttle valve opening angle is changed to the second upper-limit value. The vehicle control apparatus of the above preferred embodiment is effective in avoiding the lowering of the total output force of the vehicle even when the upper-limit value of the throttle opening angle is changed to a smaller value at the time of the malfunction determination.